Why did Europe’s Danube river freeze?

A climate pattern called a “Russian Winter”, due to the intense cold and snow triggered by a strong Siberian anticyclone hovering over northern Russia, according to a NASA statement, is keeping Europe frozen and let the Danube river has frozen. The worst of the stretch was a high of 10 F (minus 12 C) and a low of minus 11 F (minus 24 C). That was nearly 40 degrees F below normal for the day.

The Danube is a river located in Central Europe, with a leght of 2,872 km (1,785 mi) it’s the continent’s second longest river after the Volga.

Classified as an international waterway, The Danube originates in the town of Donaueschingen in the Black Forest of Germany at the confluence of the rivers Brigach and Breg. The Danube flows through 10 countries, so precise records of its last freezing are not easy to come by. But an obvious reason for this year’s freeze is the teeth-chattering cold. Taking Belgrade, Serbia, as one example, this year’s cold streak is the worst in decades, said Jim Andrews, senior meteorologist at AccuWeather.com.

In the coldest parts of the year, when the intense cooling of the surface layers of air over northeastern Siberia occurs, the time is right for the formation of a Siberian anticyclone. Also called a Siberian high, it is a semi-permanent system of high atmospheric pressure centered in northeastern Siberia. The Siberian anticyclone is one of the principal sources of polar air masses, and outbreaks of polar air westward from the high-pressure area can cause severe cold spells in the European continent.

The Danube’s freezing is just one of many severe winter events in the continent this year. Heavy snowfall has blocked roads and stranded towns in central Italy; even Venice’s famous canals froze, a rare feat. A train in Montenegro was stranded on the tracks for three days due to heavy snow.

At least four Balkan nations suspended shipping on the Danube on February 14th 2012, because of heavy ice on the river, according to news reports.

“I looked back over 20 years and found a few significant cold snaps, but I didn’t find anything quite as strong as this one,” Andrews told OurAmazingPlanet

On Jan. 13, 2003, the weather in Belgrade dropped to a low of minus 11 degrees Fahrenheit (minus 24 degrees Celsius). But two days later the temperature was back up to 47 F (8 C).